Exposure Exposed

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Entering into photography as a serious hobby often means buying an expensive camera with interchangeable lenses.  The idea behind purchasing such a thing is that a more expensive camera will produce a higher quality photo but that is not necessarily the case.  The biggest advantage of such cameras – usually referred to as “DSLRs” (which stands for “Digital Single Lens Reflex”) is the photographer’s ability to control the camera’s exposure settings.  The skill and mastery of these settings are a tremendous factor influencing the consistency of quality and artistic merit of the final photograph.

Modern DSLRs are excellent when it comes to determining exposure.  When getting the shot means everything and reaction time is essential, setting the exposure to automatic can be invaluable.  Cameras are incapable of knowing the artistic intent of the photographer, however.  The camera can also be inconsistent – even if in only small ways – which can cause difficulties.  This inconsistency is easy to demonstrate.

Try this experiment:  place your camera on a tripod and set the exposure to automatic.  Take several photos of a scene that is unchanging in lighting and content then review them.  Some will be lighter, some will be darker, and yet others may have more or less of the background in focus.  Some photos may be focused on a different part of the scene altogether.  The results are inconsistent, uncontrolled, and – depending on the photographer – unacceptable.  Mastery of the camera’s manual settings becomes key.

There are two settings manipulated by the photographer:  the camera’s Aperture and it’s Shutter Speed.

Aperture (“F”) determines how much light enters the camera per unit of time.  A larger aperture opening allows more light to enter and as smaller opening allows less light.

The counter intuitive part of the aperture is the numbering. system used  An aperture  (or F-Stop) is the ratio between the size of the aperture and the focal length of the lens.  As a result, smaller numbers represent larger apertures.  An F-Stop of 1.8 is a opening and lets in far more light than an F-Stop of 22.

Shutter speed (“t”) determines how long the sensor is exposed to light.  To acquire more light, simply open the shutter for a longer time.  To acquire less light, leave the shutter open for a shorter period of time.

There is a relationship between Aperture and the Shutter Speed, represented by a mathematical formula I wouldn’t dare ask you to memorize!  What is most important is to note the relationship between F and t and how one affects the other.  To decrease the F-stop means you must increase the shutter speed to maintain consistent exposure, and vice-versa.   Due to this relationship, determining which method to use – aperture vs. shutter speed – becomes a decision based on creative vision.

When dealing with motion, your primary tool is your shutter speed.  The faster your shutter speed, the more capable you are of freezing action.  Your aperture size will however need to increase in response.  Slower shutter speeds are a tool for creating motion blur.  Much like the faster shutter required a larger aperture, a slower shutter requires a smaller aperture.  Acquiring consistent, accurate exposures means you must be aware of this trade off.  The reason this trade off exists is that aperture does not merely determine the amount of light that enters the camera. The size of the aperture opening also determines your “Depth of Field” – or how much of the environment will be in focus.

The larger your aperture opening the less depth of field you will have and the less of the environment surrounding your subject that will be in focus. This can be particularly useful for portraits as it allows you to blur out the background and keep the viewer’s focus on your subject.

Smaller aperture openings – inversely – maximize the depth of field. This is especially useful for shooting landscapes and scenes where you wish everything to be sharply in focus from the nearest point from the camera to infinity.

The result is that freezing motion may require a lower depth of field – meaning the subject will be in focus but the background blurred. Slowing the action to create motion blurs may require that everything near and far be sharply in focus. This relationship often works to the advantage of the photographer but it is good to be aware of it.

The hobby and profession of photography both rely heavily on the mastery of its primary tool: The camera. Understanding the camera’s manual exposure settings is an essential part of that mastery providing a solid foundation supporting nearly all other aspects of photography and setting you on the path to creating more beautiful and rewarding images for years to come.

Written by J.J. Shelton